In low temperature stationary fuel cell power plants, acid electrolytes are quite common. One factor that has to be accommodated is the migration of acid from one fuel cell into the next. This has resulted in the use of acid-impermeable graphite or carbon separator plates disposed at opposite surfaces of cooler plates, or centrally within integral separator plate assemblies. In addition, cooler plates used in acid electrolyte fuel cells have had acid-impermeable edge protection layers on both edges of the cooler array, in order to avoid corrosion of the metallic coolant tube material.
In order to bond metal coolant tubes with components in typical contemporary cooler plates, the exterior surface of the coolant tubes have been roughened by flame spraying, sand blasting or otherwise. Roughening of the surface is expensive. In order to protect the coolant plate, and particularly the coolant tube, from corrosion by the acid electrolyte, contemporary cooler plates have required acid edge protection layers or films, which may have taken the form of a tape of fluorinated ethylene propylene polymer or polytetrafluoroethylene, with an adhesive layer which joins the tape to the edge of the plate; this is also expensive.
Exemplary prior systems are disclosed in U.S. Pat. Nos. 4,929,517, 5,558,955 and 6,050,331, and in patent publication US 2011-017749, all incorporated herein by reference.
Contemporary cooler plates which are disposed between flow field plates are typically not bonded or adhered to the adjacent flow field plates. While it is desirable in liquid electrolyte fuel cells to have the electrode substrates be porous and hydrophilic, so that they can act as electrolyte storage volumes, the electrolyte penetration thereof requires that there be liquid impermeable separator plates between the electrode substrates and the cooler plate to prevent coolant tube corrosion. Typically, the acid impervious graphite or carbon separator plates are bonded to the cooler plates.
The contemporary cooler plates and associated flow field plates for liquid electrolyte fuel cells are therefore composed of many parts requiring many procedural steps for their manufacture. This is not only expensive, but it also increases the bulk of each section of the fuel cell stack.